Because the computerized tomograph (hereinafter called the CT) requires projection data from multiple directions on the section of the subject under examination, an X-ray computerized tomographic scanner has an X-ray tube and X-ray detector installed on the gantry as integral parts, and revolves around the subject while collecting projection data at each specified angle of revolution. Projection data collected from multiple directions are processed by a computer to reconstruct sectional images. For surgery patients, a tomograph of the affected parts are taken before surgery to confirm the parts of patients to be operated on or to determine the method of surgery. Tomography is used after surgery to check the results. If tomography can be performed during an operation, the progress of the operation and proper treatment can be checked on the spot, which helps to determine whether the operation should be continued or terminated. Note that because a patient being operated on cannot be moved to where the CT scanner is installed, tomography during surgery was previously not possible.